As depicted in FIG. 12, in the world of digestion, the ruminant animal is one of the most diverse mammals in the world. Whereas, most mammals contain one stomach, the ruminant has four stomachs and a small intestine with a vast array of organisms with one of the most robust microbiological ecologies on the planet. In these four stomachs, it has been hypothesized that as many as 150,000 organisms reside and are prepared to digest nutritional substrates in vast quantities. The rumen ecology allows them to metamorphose bacteria that distinctly digest the substrate presentation.
Ruminants primarily digest carbon sources in the form of proteins, carbohydrates, fats, sugars and fiber. Ruminants are also unique in that the rumen ecology can ebb and flow regarding digestion and substrates and the ecology based on the substrate presentation. For example, a high corn diet will have a different ratio of bacteria, fungi, volatile fatty acids and protozoa than a high fiber diet.
Operating pH for the ruminant can range from 5.5-6.0, and up to 8.0 with the former representing a high starch/sugar diet and the latter being more fiber forage based. The rumen breaks these carbohydrates and sugars down into volatile fatty acids (VFA) in the form of acetic, lactic, propionic and butyric acid. Once they are broken down they are absorbed through the rumen wall and into the bloodstream.
Long chain fats are biohydrogenated in the rumen and absorbed in the small intestine. Crude protein substrates are hydrolyzed to peptides (chains of amino acids) and deaminated to ammonia. In a dairy animal, we find that most substrates that contribute to milk production are digested in the rumen and not post-ruminal. In a beef animal, primary concern is with digestion across the digestive tract. Post ruminal VFA's contribute less than 5% of the production a dairy animal.
Further complicating digestion by the dairy animal are the bacteria, fungi and protozoa of the rumen that contribute up to 60% of the rumen mass. Most literature and models address the production of bacteria and fungi which have a specific passage rate and a lower level of amino acid contribution. Protozoa have a 6% per hour rumen over rate and contribute up to two times higher levels of essential amino acids such as lysine and Methionine.
In contrast, most monogastric animals (i.e. pigs and chickens) have a pH site digestion in the 2-4 pH range. This allows monogastrics much greater flexibility with regard to substrate digestion starch hardness and biological efficiencies for me production. To confound the digestion efficiency in dairy, the current practices to increase corn production have increased the characteristics of corn which are detrimental to the efficiencies of lactating dairy cattle. These complexities of prolamins, particularly zein in corn can reduce the efficiency of corn up to 60-80% in the rumen and therefore reduce milk production significantly.